<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            background-color: #ccc;
        }

        .box {
            position: relative;
            width: 500px;
            height: 400px;
            background-color: #fcc;
            margin: 40px auto;
        }

        .box .byd {
            position: absolute;
            left: 50%;
            top: 50%;
            width: 8px;
            height: 8px;
            background-color: blue;
            transform: translate(-50%, -50%);
            border-radius: 50%;
        }

        .box div[class^=yy] {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            width: 8px;
            height: 8px;
            border-radius: 50%;
            box-shadow: 0 0 3px 3px blue;
            animation: key 1.2s linear infinite;
        }

        .box div.yy_2 {
            animation-delay: .4s;

        }

        .box div.yy_3 {
            animation-delay: .8s;

        }

        @keyframes key {
            0% {}

            50% {
                width: 40px;
                height: 40px;
                opacity: 1;
            }

            100% {
                width: 80px;
                height: 80px;
                opacity: 0;
            }
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="byd"></div>
        <div class="yy_1"></div>
        <div class="yy_2"></div>
        <div class="yy_3"></div>
    </div>
</body>

</html>